Motor vehicle accidents (MVAs) are extremely common in the United States, with approximately 3 million MVA's occurring every year. MVA's are also the single leading cause of posttraumatic stress disorder (PTSD) in the general population. Given the substantial associated financial costs of PTSD, it is imperative to develop effective, brief, and easily implemented treatments for MVA survivors with PTSD. Several treatments have been developed, however, many MVA survivors do not present for treatment for several reasons, including financial barriers and difficulty accessing treatment. There is also a shortage of available clinicians who are trained in evidence-based treatments for PTSD. The identification and development of a relatively inexpensive (and portable) treatment that can be implemented by a wide range of health care providers would represent a substantial public health advance. One potential intervention is the written disclosure intervention that has shown promise as an efficacious intervention in recent years. Building on a line of research conducted by the PI and funded by NIMH (R03MH068223-1A1), the goal of this project is to investigate whether written disclosure is an efficacious intervention for MVA-related PTSD. Men and women with MVA-related PTSD will be randomly assigned to either a clinic-based written disclosure intervention condition, a home-based written disclosure condition, or a supportive counseling intervention condition (standard care). Follow-up assessments will take place immediately post-treatment and at 3, 6, and 12 months following treatment. In addition to the main goal of examining the efficacy of written disclosure for PTSD, we will also examine the portability of the intervention with the inclusion on a home-based written disclosure treatment arm. In order to make additional refinement to the intervention we will investigate underlying mechanisms (e.g., physiological arousal that occurs during the writing session, narrative structure) and moderators of outcome (e.g., gender). Moreover, information gathered from patient feedback and focus groups of potential implementers will be used to make further refinements to the intervention.